<s>
An	O
embedded	B-Architecture
system	I-Architecture
is	O
a	O
computer	O
systema	O
combination	O
of	O
a	O
computer	O
processor	O
,	O
computer	B-General_Concept
memory	I-General_Concept
,	O
and	O
input/output	B-General_Concept
peripheral	O
devicesthat	O
has	O
a	O
dedicated	O
function	O
within	O
a	O
larger	O
mechanical	O
or	O
electronic	O
system	O
.	O
</s>
<s>
Because	O
an	O
embedded	B-Architecture
system	I-Architecture
typically	O
controls	O
physical	O
operations	O
of	O
the	O
machine	O
that	O
it	O
is	O
embedded	O
within	O
,	O
it	O
often	O
has	O
real-time	B-General_Concept
computing	I-General_Concept
constraints	O
.	O
</s>
<s>
Embedded	B-Architecture
systems	I-Architecture
control	O
many	O
devices	O
in	O
common	O
use	O
today	O
.	O
</s>
<s>
,	O
it	O
was	O
estimated	O
that	O
ninety-eight	O
percent	O
of	O
all	O
microprocessors	B-Architecture
manufactured	O
were	O
used	O
in	O
embedded	B-Architecture
systems	I-Architecture
.	O
</s>
<s>
Modern	O
embedded	B-Architecture
systems	I-Architecture
are	O
often	O
based	O
on	O
microcontrollers	B-Architecture
(	O
i.e.	O
</s>
<s>
microprocessors	B-Architecture
with	O
integrated	O
memory	O
and	O
peripheral	O
interfaces	B-Application
)	O
,	O
but	O
ordinary	O
microprocessors	B-Architecture
(	O
using	O
external	O
chips	O
for	O
memory	O
and	O
peripheral	O
interface	B-Application
circuits	O
)	O
are	O
also	O
common	O
,	O
especially	O
in	O
more	O
complex	O
systems	O
.	O
</s>
<s>
A	O
common	O
standard	O
class	O
of	O
dedicated	O
processors	O
is	O
the	O
digital	B-Architecture
signal	I-Architecture
processor	I-Architecture
(	O
DSP	O
)	O
.	O
</s>
<s>
Since	O
the	O
embedded	B-Architecture
system	I-Architecture
is	O
dedicated	O
to	O
specific	O
tasks	O
,	O
design	O
engineers	O
can	B-Protocol
optimize	O
it	O
to	O
reduce	O
the	O
size	O
and	O
cost	O
of	O
the	O
product	O
and	O
increase	O
its	O
reliability	O
and	O
performance	O
.	O
</s>
<s>
Some	O
embedded	B-Architecture
systems	I-Architecture
are	O
mass-produced	O
,	O
benefiting	O
from	O
economies	O
of	O
scale	O
.	O
</s>
<s>
Embedded	B-Architecture
systems	I-Architecture
range	O
in	O
size	O
from	O
portable	O
personal	O
devices	O
such	O
as	O
digital	O
watches	O
and	O
MP3	O
players	O
to	O
bigger	O
machines	O
like	O
home	O
appliances	O
,	O
industrial	O
assembly	O
lines	O
,	O
robots	B-Device
,	O
transport	O
vehicles	O
,	O
traffic	O
light	O
controllers	O
,	O
and	O
medical	B-Application
imaging	I-Application
systems	O
.	O
</s>
<s>
Large	O
installations	O
like	O
factories	O
,	O
pipelines	O
and	O
electrical	O
grids	O
rely	O
on	O
multiple	O
embedded	B-Architecture
systems	I-Architecture
networked	O
together	O
.	O
</s>
<s>
Generalized	O
through	O
software	O
customization	O
,	O
embedded	B-Architecture
systems	I-Architecture
such	O
as	O
programmable	B-Architecture
logic	I-Architecture
controllers	I-Architecture
frequently	O
comprise	O
their	O
functional	O
units	O
.	O
</s>
<s>
Embedded	B-Architecture
systems	I-Architecture
range	O
from	O
those	O
low	O
in	O
complexity	O
,	O
with	O
a	O
single	O
microcontroller	B-Architecture
chip	O
,	O
to	O
very	O
high	O
with	O
multiple	O
units	O
,	O
peripherals	O
and	O
networks	O
,	O
which	O
may	O
reside	O
in	O
equipment	B-Application
racks	I-Application
or	O
across	O
large	O
geographical	O
areas	O
connected	O
via	O
long-distance	O
communications	O
lines	O
.	O
</s>
<s>
The	O
origins	O
of	O
the	O
microprocessor	B-Architecture
and	O
the	O
microcontroller	B-Architecture
can	B-Protocol
be	O
traced	O
back	O
to	O
the	O
MOS	O
integrated	O
circuit	O
,	O
which	O
is	O
an	O
integrated	O
circuit	O
chip	O
fabricated	B-Architecture
from	O
MOSFETs	B-Architecture
(	O
metal	B-Architecture
–	I-Architecture
oxide	I-Architecture
–	I-Architecture
semiconductor	I-Architecture
field-effect	I-Architecture
transistors	I-Architecture
)	O
and	O
was	O
developed	O
in	O
the	O
early	O
1960s	O
.	O
</s>
<s>
By	O
1964	O
,	O
MOS	O
chips	O
had	O
reached	O
higher	O
transistor	B-Application
density	O
and	O
lower	O
manufacturing	O
costs	O
than	O
bipolar	O
chips	O
.	O
</s>
<s>
MOS	O
chips	O
further	O
increased	O
in	O
complexity	O
at	O
a	O
rate	O
predicted	O
by	O
Moore	O
's	O
law	O
,	O
leading	O
to	O
large-scale	O
integration	O
(	O
LSI	O
)	O
with	O
hundreds	O
of	O
transistors	B-Application
on	O
a	O
single	O
MOS	O
chip	O
by	O
the	O
late	O
1960s	O
.	O
</s>
<s>
The	O
application	O
of	O
MOS	O
LSI	O
chips	O
to	O
computing	O
was	O
the	O
basis	O
for	O
the	O
first	O
microprocessors	B-Architecture
,	O
as	O
engineers	O
began	O
recognizing	O
that	O
a	O
complete	O
computer	O
processor	O
system	O
could	O
be	O
contained	O
on	O
several	O
MOS	O
LSI	O
chips	O
.	O
</s>
<s>
The	O
first	O
multi-chip	O
microprocessors	B-Architecture
,	O
the	O
Four-Phase	O
Systems	O
AL1	O
in	O
1969	O
and	O
the	O
Garrett	O
AiResearch	O
MP944	B-Device
in	O
1970	O
,	O
were	O
developed	O
with	O
multiple	O
MOS	O
LSI	O
chips	O
.	O
</s>
<s>
The	O
first	O
single-chip	O
microprocessor	B-Architecture
was	O
the	O
Intel	B-General_Concept
4004	I-General_Concept
,	O
released	O
in	O
1971	O
.	O
</s>
<s>
It	O
was	O
developed	O
by	O
Federico	O
Faggin	O
,	O
using	O
his	O
silicon-gate	O
MOS	B-Architecture
technology	I-Architecture
,	O
along	O
with	O
Intel	O
engineers	O
Marcian	O
Hoff	O
and	O
Stan	O
Mazor	O
,	O
and	O
Busicom	O
engineer	O
Masatoshi	O
Shima	O
.	O
</s>
<s>
One	O
of	O
the	O
first	O
recognizably	O
modern	O
embedded	B-Architecture
systems	I-Architecture
was	O
the	O
Apollo	B-Application
Guidance	I-Application
Computer	I-Application
,	O
developed	O
ca	O
.	O
</s>
<s>
At	O
the	O
project	O
's	O
inception	O
,	O
the	O
Apollo	B-Application
guidance	I-Application
computer	I-Application
was	O
considered	O
the	O
riskiest	O
item	O
in	O
the	O
Apollo	O
project	O
as	O
it	O
employed	O
the	O
then	O
newly	O
developed	O
monolithic	O
integrated	O
circuits	O
to	O
reduce	O
the	O
computer	O
's	O
size	O
and	O
weight	O
.	O
</s>
<s>
An	O
early	O
mass-produced	O
embedded	B-Architecture
system	I-Architecture
was	O
the	O
Autonetics	B-Device
D-17	I-Device
guidance	I-Device
computer	I-Device
for	O
the	O
Minuteman	O
missile	O
,	O
released	O
in	O
1961	O
.	O
</s>
<s>
Since	O
these	O
early	O
applications	O
in	O
the	O
1960s	O
,	O
embedded	B-Architecture
systems	I-Architecture
have	O
come	O
down	O
in	O
price	O
and	O
there	O
has	O
been	O
a	O
dramatic	O
rise	O
in	O
processing	O
power	O
and	O
functionality	O
.	O
</s>
<s>
An	O
early	O
microprocessor	B-Architecture
,	O
the	O
Intel	B-General_Concept
4004	I-General_Concept
(	O
released	O
in	O
1971	O
)	O
,	O
was	O
designed	O
for	O
calculators	B-Application
and	O
other	O
small	O
systems	O
but	O
still	O
required	O
external	O
memory	O
and	O
support	O
chips	O
.	O
</s>
<s>
By	O
the	O
early	O
1980s	O
,	O
memory	O
,	O
input	B-General_Concept
and	I-General_Concept
output	I-General_Concept
system	O
components	O
had	O
been	O
integrated	O
into	O
the	O
same	O
chip	O
as	O
the	O
processor	O
forming	O
a	O
microcontroller	B-Architecture
.	O
</s>
<s>
Microcontrollers	B-Architecture
find	O
applications	O
where	O
a	O
general-purpose	O
computer	O
would	O
be	O
too	O
costly	O
.	O
</s>
<s>
As	O
the	O
cost	O
of	O
microprocessors	B-Architecture
and	O
microcontrollers	B-Architecture
fell	O
,	O
the	O
prevalence	O
of	O
embedded	B-Architecture
systems	I-Architecture
increased	O
.	O
</s>
<s>
Today	O
,	O
a	O
comparatively	O
low-cost	O
microcontroller	B-Architecture
may	O
be	O
programmed	O
to	O
fulfill	O
the	O
same	O
role	O
as	O
a	O
large	O
number	O
of	O
separate	O
components	O
.	O
</s>
<s>
With	O
microcontrollers	B-Architecture
,	O
it	O
became	O
feasible	O
to	O
replace	O
,	O
even	O
in	O
consumer	O
products	O
,	O
expensive	O
knob-based	O
analog	O
components	O
such	O
as	O
potentiometers	B-Device
and	O
variable	O
capacitors	O
with	O
up/down	O
buttons	O
or	O
knobs	O
read	O
out	O
by	O
a	O
microprocessor	B-Architecture
.	O
</s>
<s>
Although	O
in	O
this	O
context	O
an	O
embedded	B-Architecture
system	I-Architecture
is	O
usually	O
more	O
complex	O
than	O
a	O
traditional	O
solution	O
,	O
most	O
of	O
the	O
complexity	O
is	O
contained	O
within	O
the	O
microcontroller	B-Architecture
itself	O
.	O
</s>
<s>
Software	O
prototype	O
and	O
test	O
can	B-Protocol
be	O
quicker	O
compared	O
with	O
the	O
design	O
and	O
construction	O
of	O
a	O
new	O
circuit	O
not	O
using	O
an	O
embedded	B-Architecture
processor	I-Architecture
.	O
</s>
<s>
Embedded	B-Architecture
systems	I-Architecture
are	O
commonly	O
found	O
in	O
consumer	O
,	O
industrial	O
,	O
automotive	O
,	O
home	O
appliances	O
,	O
medical	O
,	O
telecommunication	O
,	O
commercial	O
,	O
aerospace	O
and	O
military	O
applications	O
.	O
</s>
<s>
Telecommunications	O
systems	O
employ	O
numerous	O
embedded	B-Architecture
systems	I-Architecture
from	O
telephone	O
switches	O
for	O
the	O
network	O
to	O
cell	O
phones	O
at	O
the	O
end	O
user	O
.	O
</s>
<s>
Computer	O
networking	O
uses	O
dedicated	O
routers	B-Protocol
and	O
network	B-Protocol
bridges	I-Protocol
to	O
route	O
data	O
.	O
</s>
<s>
Consumer	O
electronics	O
include	O
MP3	O
players	O
,	O
television	O
sets	O
,	O
mobile	O
phones	O
,	O
video	B-Device
game	I-Device
consoles	I-Device
,	O
digital	B-Device
cameras	I-Device
,	O
GPS	O
receivers	O
,	O
and	O
printers	O
.	O
</s>
<s>
Household	O
appliances	O
,	O
such	O
as	O
microwave	O
ovens	O
,	O
washing	O
machines	O
and	O
dishwashers	B-Application
,	O
include	O
embedded	B-Architecture
systems	I-Architecture
to	O
provide	O
flexibility	O
,	O
efficiency	O
and	O
features	O
.	O
</s>
<s>
Advanced	O
heating	O
,	O
ventilation	O
,	O
and	O
air	O
conditioning	O
(	O
HVAC	O
)	O
systems	O
use	O
networked	O
thermostats	O
to	O
more	O
accurately	O
and	O
efficiently	O
control	O
temperature	O
that	O
can	B-Protocol
change	O
by	O
time	O
of	O
day	O
and	O
season	O
.	O
</s>
<s>
Home	O
automation	O
uses	O
wired	O
-	O
and	O
wireless-networking	O
that	O
can	B-Protocol
be	O
used	O
to	O
control	O
lights	O
,	O
climate	O
,	O
security	O
,	O
audio/visual	O
,	O
surveillance	O
,	O
etc.	O
,	O
all	O
of	O
which	O
use	O
embedded	B-Architecture
devices	I-Architecture
for	O
sensing	O
and	O
controlling	O
.	O
</s>
<s>
Transportation	O
systems	O
from	O
flight	O
to	O
automobiles	O
increasingly	O
use	O
embedded	B-Architecture
systems	I-Architecture
.	O
</s>
<s>
Automobiles	O
,	O
electric	O
vehicles	O
,	O
and	O
hybrid	O
vehicles	O
increasingly	O
use	O
embedded	B-Architecture
systems	I-Architecture
to	O
maximize	O
efficiency	O
and	O
reduce	O
pollution	O
.	O
</s>
<s>
Other	O
automotive	O
safety	O
systems	O
using	O
embedded	B-Architecture
systems	I-Architecture
include	O
anti-lock	O
braking	O
system	O
(	O
ABS	O
)	O
,	O
electronic	O
stability	O
control	O
(	O
ESC/ESP	O
)	O
,	O
traction	O
control	O
(	O
TCS	O
)	O
and	O
automatic	O
four-wheel	O
drive	O
.	O
</s>
<s>
Medical	O
equipment	O
uses	O
embedded	B-Architecture
systems	I-Architecture
for	O
monitoring	O
,	O
and	O
various	O
medical	B-Application
imaging	I-Application
(	O
positron	B-Application
emission	I-Application
tomography	I-Application
(	O
PET	O
)	O
,	O
single-photon	O
emission	O
computed	O
tomography	O
(	O
SPECT	O
)	O
,	O
computed	O
tomography	O
(	O
CT	O
)	O
,	O
and	O
magnetic	O
resonance	O
imaging	O
(	O
MRI	O
)	O
for	O
non-invasive	O
internal	O
inspections	O
.	O
</s>
<s>
Embedded	B-Architecture
systems	I-Architecture
within	O
medical	O
equipment	O
are	O
often	O
powered	O
by	O
industrial	B-Architecture
computers	I-Architecture
.	O
</s>
<s>
Embedded	B-Architecture
systems	I-Architecture
are	O
used	O
for	O
safety-critical	B-Application
systems	I-Application
in	O
aerospace	O
and	O
defense	O
industries	O
.	O
</s>
<s>
Unless	O
connected	O
to	O
wired	O
or	O
wireless	O
networks	O
via	O
on-chip	O
3G	O
cellular	O
or	O
other	O
methods	O
for	O
IoT	O
monitoring	O
and	O
control	O
purposes	O
,	O
these	O
systems	O
can	B-Protocol
be	O
isolated	O
from	O
hacking	O
and	O
thus	O
be	O
more	O
secure	O
.	O
</s>
<s>
For	O
fire	O
safety	O
,	O
the	O
systems	O
can	B-Protocol
be	O
designed	O
to	O
have	O
a	O
greater	O
ability	O
to	O
handle	O
higher	O
temperatures	O
and	O
continue	O
to	O
operate	O
.	O
</s>
<s>
In	O
dealing	O
with	O
security	O
,	O
the	O
embedded	B-Architecture
systems	I-Architecture
can	B-Protocol
be	O
self-sufficient	O
and	O
be	O
able	O
to	O
deal	O
with	O
cut	O
electrical	O
and	O
communication	O
systems	O
.	O
</s>
<s>
Miniature	O
wireless	O
devices	O
called	O
motes	B-Device
are	O
networked	O
wireless	B-Architecture
sensors	I-Architecture
.	O
</s>
<s>
Wireless	B-Architecture
sensor	I-Architecture
networking	I-Architecture
makes	O
use	O
of	O
miniaturization	O
made	O
possible	O
by	O
advanced	O
integrated	O
circuit	O
(	O
IC	O
)	O
design	O
to	O
couple	O
full	O
wireless	O
subsystems	O
to	O
sophisticated	O
sensors	O
,	O
enabling	O
people	O
and	O
companies	O
to	O
measure	O
a	O
myriad	O
of	O
things	O
in	O
the	O
physical	O
world	O
and	O
act	O
on	O
this	O
information	O
through	O
monitoring	O
and	O
control	O
systems	O
.	O
</s>
<s>
These	O
motes	B-Device
are	O
completely	O
self-contained	O
and	O
will	O
typically	O
run	O
off	O
a	O
battery	O
source	O
for	O
years	O
before	O
the	O
batteries	O
need	O
to	O
be	O
changed	O
or	O
charged	O
.	O
</s>
<s>
Embedded	B-Architecture
systems	I-Architecture
are	O
designed	O
to	O
do	O
some	O
specific	O
task	O
,	O
rather	O
than	O
be	O
a	O
general-purpose	O
computer	O
for	O
multiple	O
tasks	O
.	O
</s>
<s>
Some	O
also	O
have	O
real-time	B-General_Concept
performance	O
constraints	O
that	O
must	O
be	O
met	O
,	O
for	O
reasons	O
such	O
as	O
safety	O
and	O
usability	O
;	O
others	O
may	O
have	O
low	O
or	O
no	O
performance	O
requirements	O
,	O
allowing	O
the	O
system	O
hardware	O
to	O
be	O
simplified	O
to	O
reduce	O
costs	O
.	O
</s>
<s>
Embedded	B-Architecture
systems	I-Architecture
are	O
not	O
always	O
standalone	O
devices	O
.	O
</s>
<s>
Many	O
embedded	B-Architecture
systems	I-Architecture
consist	O
of	O
small	O
parts	O
within	O
a	O
larger	O
device	O
that	O
serves	O
a	O
more	O
general	O
purpose	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
Gibson	O
Robot	O
Guitar	O
features	O
an	O
embedded	B-Architecture
system	I-Architecture
for	O
tuning	O
the	O
strings	O
,	O
but	O
the	O
overall	O
purpose	O
of	O
the	O
Robot	O
Guitar	O
is	O
to	O
play	O
music	O
.	O
</s>
<s>
Similarly	O
,	O
an	O
embedded	B-Architecture
system	I-Architecture
in	O
an	O
automobile	O
provides	O
a	O
specific	O
function	O
as	O
a	O
subsystem	O
of	O
the	O
car	O
itself	O
.	O
</s>
<s>
The	O
program	O
instructions	O
written	O
for	O
embedded	B-Architecture
systems	I-Architecture
are	O
referred	O
to	O
as	O
firmware	B-Application
,	O
and	O
are	O
stored	O
in	O
read-only	O
memory	O
or	O
flash	B-Device
memory	I-Device
chips	O
.	O
</s>
<s>
Embedded	B-Architecture
systems	I-Architecture
range	O
from	O
no	B-Application
user	I-Application
interface	I-Application
at	O
all	O
,	O
in	O
systems	O
dedicated	O
only	O
to	O
one	O
task	O
,	O
to	O
complex	O
graphical	B-Application
user	I-Application
interfaces	I-Application
that	O
resemble	O
modern	O
computer	O
desktop	O
operating	O
systems	O
.	O
</s>
<s>
Simple	O
embedded	B-Architecture
devices	I-Architecture
use	O
buttons	O
,	O
light-emitting	O
diodes	O
(	O
LED	O
)	O
,	O
graphic	O
or	O
character	O
liquid-crystal	B-Device
displays	I-Device
(	O
LCD	B-Device
)	O
with	O
a	O
simple	O
menu	O
system	O
.	O
</s>
<s>
More	O
sophisticated	O
devices	O
that	O
use	O
a	O
graphical	O
screen	O
with	O
touch	B-Device
sensing	I-Device
or	O
screen-edge	O
soft	B-General_Concept
keys	I-General_Concept
provide	O
flexibility	O
while	O
minimizing	O
space	O
used	O
:	O
the	O
meaning	O
of	O
the	O
buttons	O
can	B-Protocol
change	O
with	O
the	O
screen	O
,	O
and	O
selection	O
involves	O
the	O
natural	O
behavior	O
of	O
pointing	O
at	O
what	O
is	O
desired	O
.	O
</s>
<s>
Some	O
systems	O
provide	O
user	O
interface	B-Application
remotely	O
with	O
the	O
help	O
of	O
a	O
serial	O
(	O
e.g.	O
</s>
<s>
This	O
approach	O
extends	O
the	O
capabilities	O
of	O
the	O
embedded	B-Architecture
system	I-Architecture
,	O
avoids	O
the	O
cost	O
of	O
a	O
display	O
,	O
simplifies	O
the	O
board	B-Operating_System
support	I-Operating_System
package	I-Operating_System
(	O
BSP	O
)	O
and	O
allows	O
designers	O
to	O
build	O
a	O
rich	O
user	O
interface	B-Application
on	O
the	O
PC	O
.	O
</s>
<s>
A	O
good	O
example	O
of	O
this	O
is	O
the	O
combination	O
of	O
an	O
embedded	B-Protocol
HTTP	I-Protocol
server	I-Protocol
running	O
on	O
an	O
embedded	B-Architecture
device	I-Architecture
(	O
such	O
as	O
an	O
IP	B-Algorithm
camera	I-Algorithm
or	O
a	O
network	B-Protocol
router	I-Protocol
)	O
.	O
</s>
<s>
The	O
user	O
interface	B-Application
is	O
displayed	O
in	O
a	O
web	B-Application
browser	I-Application
on	O
a	O
PC	O
connected	O
to	O
the	O
device	O
.	O
</s>
<s>
Examples	O
of	O
properties	O
of	O
typical	O
embedded	B-Architecture
computers	I-Architecture
when	O
compared	O
with	O
general-purpose	O
counterparts	O
,	O
are	O
low	O
power	O
consumption	O
,	O
small	O
size	O
,	O
rugged	O
operating	O
ranges	O
,	O
and	O
low	O
per-unit	O
cost	O
.	O
</s>
<s>
Numerous	B-Device
microcontrollers	I-Device
have	O
been	O
developed	O
for	O
embedded	B-Architecture
systems	I-Architecture
use	O
.	O
</s>
<s>
General-purpose	O
microprocessors	B-Architecture
are	O
also	O
used	O
in	O
embedded	B-Architecture
systems	I-Architecture
,	O
but	O
generally	O
,	O
require	O
more	O
support	O
circuitry	O
than	O
microcontrollers	B-Architecture
.	O
</s>
<s>
PC/104	B-Device
and	O
PC/104	B-Device
+	O
are	O
examples	O
of	O
standards	O
for	O
ready-made	O
computer	O
boards	O
intended	O
for	O
small	O
,	O
low-volume	O
embedded	O
and	O
ruggedized	O
systems	O
.	O
</s>
<s>
These	O
are	O
mostly	O
x86-based	O
and	O
often	O
physically	O
small	O
compared	O
to	O
a	O
standard	O
PC	O
,	O
although	O
still	O
quite	O
large	O
compared	O
to	O
most	O
simple	O
(	O
8/16	O
-bit	O
)	O
embedded	B-Architecture
systems	I-Architecture
.	O
</s>
<s>
They	O
may	O
use	O
DOS	B-Device
,	O
Linux	B-Application
,	O
NetBSD	B-Device
,	O
or	O
an	O
embedded	O
real-time	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
(	O
RTOS	B-Operating_System
)	O
such	O
as	O
MicroC/OS	B-Operating_System
-II	I-Operating_System
,	O
QNX	B-Operating_System
or	O
VxWorks	B-Operating_System
.	O
</s>
<s>
Boards	O
such	O
as	O
the	O
VIA	B-Device
EPIA	I-Device
range	O
help	O
to	O
bridge	O
the	O
gap	O
by	O
being	O
PC-compatible	O
but	O
highly	O
integrated	O
,	O
physically	O
smaller	O
or	O
have	O
other	O
attributes	O
making	O
them	O
attractive	O
to	O
embedded	B-Architecture
engineers	I-Architecture
.	O
</s>
<s>
The	O
advantage	O
of	O
this	O
approach	O
is	O
that	O
low-cost	O
commodity	O
components	O
may	O
be	O
used	O
along	O
with	O
the	O
same	O
software	O
development	O
tools	B-Application
used	O
for	O
general	O
software	O
development	O
.	O
</s>
<s>
However	O
,	O
most	O
ready-made	O
embedded	B-Architecture
systems	I-Architecture
boards	O
are	O
not	O
PC-centered	O
and	O
do	O
not	O
use	O
the	O
ISA	B-Architecture
or	O
PCI	B-Protocol
busses	O
.	O
</s>
<s>
When	O
a	O
system-on-a-chip	B-Architecture
processor	O
is	O
involved	O
,	O
there	O
may	O
be	O
little	O
benefit	O
to	O
having	O
a	O
standardized	O
bus	O
connecting	O
discrete	O
components	O
,	O
and	O
the	O
environment	O
for	O
both	O
hardware	O
and	O
software	O
tools	B-Application
may	O
be	O
very	O
different	O
.	O
</s>
<s>
One	O
common	O
design	O
style	O
uses	O
a	O
small	O
system	O
module	O
,	O
perhaps	O
the	O
size	O
of	O
a	O
business	O
card	O
,	O
holding	O
high	O
density	O
BGA	B-Algorithm
chips	O
such	O
as	O
an	O
ARM-based	O
system-on-a-chip	B-Architecture
processor	O
and	O
peripherals	O
,	O
external	O
flash	B-Device
memory	I-Device
for	O
storage	O
,	O
and	O
DRAM	O
for	O
runtime	O
memory	O
.	O
</s>
<s>
The	O
module	O
vendor	O
will	O
usually	O
provide	O
boot	O
software	O
and	O
make	O
sure	O
there	O
is	O
a	O
selection	O
of	O
operating	O
systems	O
,	O
usually	O
including	O
Linux	B-Application
and	O
some	O
real-time	B-General_Concept
choices	O
.	O
</s>
<s>
These	O
modules	O
can	B-Protocol
be	O
manufactured	O
in	O
high	O
volume	O
,	O
by	O
organizations	O
familiar	O
with	O
their	O
specialized	O
testing	O
issues	O
,	O
and	O
combined	O
with	O
much	O
lower	O
volume	O
custom	O
mainboards	O
with	O
application-specific	O
external	O
peripherals	O
.	O
</s>
<s>
Prominent	O
examples	O
of	O
this	O
approach	O
include	O
Arduino	O
and	O
Raspberry	B-Operating_System
Pi	I-Operating_System
.	O
</s>
<s>
A	O
system	B-Architecture
on	I-Architecture
a	I-Architecture
chip	I-Architecture
(	O
SoC	O
)	O
contains	O
a	O
complete	O
system	O
-	O
consisting	O
of	O
multiple	O
processors	O
,	O
multipliers	O
,	O
caches	O
,	O
even	O
different	O
types	O
of	O
memory	O
and	O
commonly	O
various	O
peripherals	O
like	O
interfaces	B-Application
for	O
wired	O
or	O
wireless	O
communication	O
on	O
a	O
single	O
chip	O
.	O
</s>
<s>
SoCs	O
can	B-Protocol
be	O
implemented	O
as	O
an	O
application-specific	O
integrated	O
circuit	O
(	O
ASIC	O
)	O
or	O
using	O
a	O
field-programmable	B-Architecture
gate	I-Architecture
array	I-Architecture
(	O
FPGA	B-Architecture
)	O
which	O
typically	O
can	B-Protocol
be	O
reconfigured	O
.	O
</s>
<s>
ASIC	O
implementations	O
are	O
common	O
for	O
very-high-volume	O
embedded	B-Architecture
systems	I-Architecture
like	O
mobile	O
phones	O
and	O
smartphones	B-Application
.	O
</s>
<s>
ASIC	O
or	O
FPGA	B-Architecture
implementations	O
may	O
be	O
used	O
for	O
not-so-high-volume	O
embedded	B-Architecture
systems	I-Architecture
with	O
special	O
needs	O
in	O
kind	O
of	O
signal	O
processing	O
performance	O
,	O
interfaces	B-Application
and	O
reliability	O
,	O
like	O
in	O
avionics	O
.	O
</s>
<s>
Embedded	B-Architecture
systems	I-Architecture
talk	O
with	O
the	O
outside	O
world	O
via	O
peripherals	O
,	O
such	O
as	O
:	O
</s>
<s>
Serial	O
communication	O
interfaces	B-Application
(	O
SCI	O
)	O
:	O
RS-232	O
,	O
RS-422	O
,	O
RS-485	O
,	O
etc	O
.	O
</s>
<s>
Media	O
cards	O
(	O
SD	B-Device
cards	I-Device
,	O
CompactFlash	B-Device
,	O
etc	O
.	O
)	O
</s>
<s>
Network	B-Protocol
interface	I-Protocol
controller	I-Protocol
:	O
Ethernet	O
,	O
WiFi	O
,	O
etc	O
.	O
</s>
<s>
Fieldbuses	O
:	O
CAN	B-Protocol
bus	I-Protocol
,	O
LIN-Bus	O
,	O
PROFIBUS	O
,	O
etc	O
.	O
</s>
<s>
Debugging	O
:	O
JTAG	O
,	O
In-system	B-Device
programming	I-Device
,	O
background	B-Application
debug	I-Application
mode	I-Application
interface	I-Application
port	O
,	O
BITP	O
,	O
and	O
DB9	O
ports	O
.	O
</s>
<s>
As	O
with	O
other	O
software	O
,	O
embedded	B-Architecture
system	I-Architecture
designers	O
use	O
compilers	B-Language
,	O
assemblers	B-Language
,	O
and	O
debuggers	B-Application
to	O
develop	O
embedded	B-Architecture
system	I-Architecture
software	O
.	O
</s>
<s>
However	O
,	O
they	O
may	O
also	O
use	O
more	O
specific	O
tools	B-Application
:	O
</s>
<s>
In	O
circuit	O
debuggers	B-Application
or	O
emulators	B-Application
(	O
see	O
next	O
section	O
)	O
.	O
</s>
<s>
Utilities	O
to	O
add	O
a	O
checksum	O
or	O
CRC	O
to	O
a	O
program	O
,	O
so	O
the	O
embedded	B-Architecture
system	I-Architecture
can	B-Protocol
check	O
if	O
the	O
program	O
is	O
valid	O
.	O
</s>
<s>
For	O
systems	O
using	O
digital	B-General_Concept
signal	I-General_Concept
processing	I-General_Concept
,	O
developers	O
may	O
use	O
a	O
computational	B-Application
notebook	I-Application
to	O
simulate	O
the	O
mathematics	O
.	O
</s>
<s>
System-level	O
modeling	O
and	O
simulation	O
tools	B-Application
help	O
designers	O
to	O
construct	O
simulation	O
models	O
of	O
a	O
system	O
with	O
hardware	O
components	O
such	O
as	O
processors	O
,	O
memories	O
,	O
DMA	B-General_Concept
,	O
interfaces	B-Application
,	O
buses	O
and	O
software	O
behavior	O
flow	O
as	O
a	O
state	O
diagram	O
or	O
flow	O
diagram	O
using	O
configurable	O
library	O
blocks	O
.	O
</s>
<s>
A	O
model-based	O
development	O
tool	O
creates	O
and	O
simulates	O
graphical	O
data	O
flow	O
and	O
UML	B-Application
state	I-Application
chart	I-Application
diagrams	O
of	O
components	O
like	O
digital	O
filters	O
,	O
motor	O
controllers	O
,	O
communication	O
protocol	O
decoding	O
and	O
multi-rate	O
tasks	O
.	O
</s>
<s>
Custom	O
compilers	B-Language
and	O
linkers	O
may	O
be	O
used	O
to	O
optimize	O
specialized	O
hardware	O
.	O
</s>
<s>
An	O
embedded	B-Architecture
system	I-Architecture
may	O
have	O
its	O
own	O
special	O
language	O
or	O
design	O
tool	O
,	O
or	O
add	O
enhancements	O
to	O
an	O
existing	O
language	O
such	O
as	O
Forth	B-Application
or	O
Basic	B-Language
.	O
</s>
<s>
Software	O
tools	B-Application
can	B-Protocol
come	O
from	O
several	O
sources	O
:	O
</s>
<s>
As	O
the	O
complexity	O
of	O
embedded	B-Architecture
systems	I-Architecture
grows	O
,	O
higher-level	O
tools	B-Application
and	O
operating	O
systems	O
are	O
migrating	O
into	O
machinery	O
where	O
it	O
makes	O
sense	O
.	O
</s>
<s>
For	O
example	O
,	O
cellphones	O
,	O
personal	B-Application
digital	I-Application
assistants	I-Application
and	O
other	O
consumer	O
computers	O
often	O
need	O
significant	O
software	O
that	O
is	O
purchased	O
or	O
provided	O
by	O
a	O
person	O
other	O
than	O
the	O
manufacturer	O
of	O
the	O
electronics	O
.	O
</s>
<s>
In	O
these	O
systems	O
,	O
an	O
open	O
programming	B-Application
environment	I-Application
such	O
as	O
Linux	B-Application
,	O
NetBSD	B-Device
,	O
OSGi	B-Application
or	O
Embedded	B-Language
Java	I-Language
is	O
required	O
so	O
that	O
the	O
third-party	O
software	O
provider	O
can	B-Protocol
sell	O
to	O
a	O
large	O
market	O
.	O
</s>
<s>
Considerations	O
include	O
:	O
does	O
it	O
slow	O
down	O
the	O
main	O
application	O
,	O
how	O
close	O
is	O
the	O
debugged	O
system	O
or	O
application	O
to	O
the	O
actual	O
system	O
or	O
application	O
,	O
how	O
expressive	O
are	O
the	O
triggers	O
that	O
can	B-Protocol
be	O
set	O
for	O
debugging	O
(	O
e.g.	O
,	O
inspecting	O
the	O
memory	O
when	O
a	O
particular	O
program	B-General_Concept
counter	I-General_Concept
value	O
is	O
reached	O
)	O
,	O
and	O
what	O
can	B-Protocol
be	O
inspected	O
in	O
the	O
debugging	O
process	O
(	O
such	O
as	O
,	O
only	O
memory	O
,	O
or	O
memory	O
and	O
registers	O
,	O
etc	O
.	O
</s>
<s>
Interactive	O
resident	O
debugging	O
,	O
using	O
the	O
simple	O
shell	O
provided	O
by	O
the	O
embedded	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
(	O
e.g.	O
</s>
<s>
Software-only	O
debuggers	B-Application
have	O
the	O
benefit	O
that	O
they	O
do	O
not	O
need	O
any	O
hardware	O
modification	O
but	O
have	O
to	O
carefully	O
control	O
what	O
they	O
record	O
in	O
order	O
to	O
conserve	O
time	O
and	O
storage	O
space	O
.	O
</s>
<s>
External	O
debugging	O
using	O
logging	O
or	O
serial	O
port	O
output	O
to	O
trace	O
operation	O
using	O
either	O
a	O
monitor	O
in	O
flash	O
or	O
using	O
a	O
debug	O
server	O
like	O
the	O
Remedy	B-Application
Debugger	I-Application
that	O
even	O
works	O
for	O
heterogeneous	O
multicore	B-Architecture
systems	O
.	O
</s>
<s>
An	O
in-circuit	B-Application
debugger	I-Application
(	O
ICD	O
)	O
,	O
a	O
hardware	O
device	O
that	O
connects	O
to	O
the	O
microprocessor	B-Architecture
via	O
a	O
JTAG	O
or	O
Nexus	O
interface	B-Application
.	O
</s>
<s>
This	O
allows	O
the	O
operation	O
of	O
the	O
microprocessor	B-Architecture
to	O
be	O
controlled	O
externally	O
,	O
but	O
is	O
typically	O
restricted	O
to	O
specific	O
debugging	O
capabilities	O
in	O
the	O
processor	O
.	O
</s>
<s>
An	O
in-circuit	B-Application
emulator	I-Application
(	O
ICE	O
)	O
replaces	O
the	O
microprocessor	B-Architecture
with	O
a	O
simulated	O
equivalent	O
,	O
providing	O
full	O
control	O
over	O
all	O
aspects	O
of	O
the	O
microprocessor	B-Architecture
.	O
</s>
<s>
A	O
complete	O
emulator	B-Application
provides	O
a	O
simulation	O
of	O
all	O
aspects	O
of	O
the	O
hardware	O
,	O
allowing	O
all	O
of	O
it	O
to	O
be	O
controlled	O
and	O
modified	O
,	O
and	O
allowing	O
debugging	O
on	O
a	O
normal	O
PC	O
.	O
</s>
<s>
For	O
SoC	O
designs	O
,	O
the	O
typical	O
approach	O
is	O
to	O
verify	O
and	O
debug	O
the	O
design	O
on	O
an	O
FPGA	B-Architecture
prototype	O
board	O
.	O
</s>
<s>
Tools	B-Application
such	O
as	O
Certus	O
are	O
used	O
to	O
insert	O
probes	O
in	O
the	O
FPGA	B-Architecture
implementation	O
that	O
make	O
signals	O
available	O
for	O
observation	O
.	O
</s>
<s>
This	O
is	O
used	O
to	O
debug	O
hardware	O
,	O
firmware	B-Application
and	O
software	O
interactions	O
across	O
multiple	O
FPGAs	B-Architecture
in	O
an	O
implementation	O
with	O
capabilities	O
similar	O
to	O
a	O
logic	O
analyzer	O
.	O
</s>
<s>
Unless	O
restricted	O
to	O
external	O
debugging	O
,	O
the	O
programmer	O
can	B-Protocol
typically	O
load	O
and	O
run	O
software	O
through	O
the	O
tools	B-Application
,	O
view	O
the	O
code	O
running	O
in	O
the	O
processor	O
,	O
and	O
start	O
or	O
stop	O
its	O
operation	O
.	O
</s>
<s>
The	O
view	O
of	O
the	O
code	O
may	O
be	O
as	O
high-level	B-Language
programming	I-Language
language	I-Language
,	O
assembly	B-Language
code	I-Language
or	O
mixture	O
of	O
both	O
.	O
</s>
<s>
Real-time	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
often	O
support	O
tracing	O
of	O
operating	O
system	O
events	O
.	O
</s>
<s>
The	O
trace	O
recording	O
can	B-Protocol
be	O
performed	O
in	O
software	O
,	O
by	O
the	O
RTOS	B-Operating_System
,	O
or	O
by	O
special	O
tracing	O
hardware	O
.	O
</s>
<s>
RTOS	B-Operating_System
tracing	O
allows	O
developers	O
to	O
understand	O
timing	O
and	O
performance	O
issues	O
of	O
the	O
software	O
system	O
and	O
gives	O
a	O
good	O
understanding	O
of	O
the	O
high-level	O
system	O
behaviors	O
.	O
</s>
<s>
Trace	O
recording	O
in	O
embedded	B-Architecture
systems	I-Architecture
can	B-Protocol
be	O
achieved	O
using	O
hardware	O
or	O
software	O
solutions	O
.	O
</s>
<s>
Software-based	O
trace	O
recording	O
does	O
not	O
require	O
specialized	O
debugging	O
hardware	O
and	O
can	B-Protocol
be	O
used	O
to	O
record	O
traces	O
in	O
deployed	O
devices	O
,	O
but	O
it	O
can	B-Protocol
have	O
an	O
impact	O
on	O
CPU	O
and	O
RAM	O
usage	O
.	O
</s>
<s>
One	O
example	O
of	O
a	O
software-based	O
tracing	O
method	O
used	O
in	O
RTOS	B-Operating_System
environments	O
is	O
the	O
use	O
of	O
empty	O
macros	O
which	O
are	O
invoked	O
by	O
the	O
operating	O
system	O
at	O
strategic	O
places	O
in	O
the	O
code	O
,	O
and	O
can	B-Protocol
be	O
implemented	O
to	O
serve	O
as	O
hooks	O
.	O
</s>
<s>
Embedded	B-Architecture
systems	I-Architecture
often	O
reside	O
in	O
machines	O
that	O
are	O
expected	O
to	O
run	O
continuously	O
for	O
years	O
without	O
error	O
,	O
and	O
in	O
some	O
cases	O
recover	O
by	O
themselves	O
if	O
an	O
error	O
occurs	O
.	O
</s>
<s>
Examples	O
include	O
aircraft	O
navigation	O
,	O
reactor	O
control	O
systems	O
,	O
safety-critical	B-Application
chemical	O
factory	O
controls	O
,	O
train	O
signals	O
.	O
</s>
<s>
A	O
variety	O
of	O
techniques	O
are	O
used	O
,	O
sometimes	O
in	O
combination	O
,	O
to	O
recover	O
from	O
errors	O
—	O
both	O
software	O
bugs	O
such	O
as	O
memory	B-Error_Name
leaks	I-Error_Name
,	O
and	O
also	O
soft	O
errors	O
in	O
the	O
hardware	O
:	O
</s>
<s>
A	O
hypervisor	B-Operating_System
designed	O
for	O
embedded	B-Architecture
systems	I-Architecture
is	O
able	O
to	O
provide	O
secure	O
encapsulation	O
for	O
any	O
subsystem	O
component	O
so	O
that	O
a	O
compromised	O
software	O
component	O
cannot	O
interfere	O
with	O
other	O
subsystems	O
,	O
or	O
privileged-level	O
system	O
software	O
.	O
</s>
<s>
Immunity-aware	O
programming	O
can	B-Protocol
help	O
engineers	O
produce	O
more	O
reliable	O
embedded	B-Architecture
systems	I-Architecture
code	O
.	O
</s>
<s>
Guidelines	O
and	O
coding	O
rules	O
such	O
as	O
MISRA	B-Language
C/C	I-Language
++	I-Language
aim	O
to	O
assist	O
developers	O
produce	O
reliable	O
,	O
portable	O
firmware	B-Application
in	O
a	O
number	O
of	O
different	O
ways	O
:	O
typically	O
by	O
advising	O
or	O
mandating	O
against	O
coding	O
practices	O
which	O
may	O
lead	O
to	O
run-time	O
errors	O
(	O
memory	B-Error_Name
leaks	I-Error_Name
,	O
invalid	O
pointer	O
uses	O
)	O
,	O
use	O
of	O
run-time	O
checks	O
and	O
exception	O
handling	O
(	O
range/sanity	O
checks	O
,	O
divide-by-zero	O
and	O
buffer	O
index	O
validity	O
checks	O
,	O
default	O
cases	O
in	O
logic	O
checks	O
)	O
,	O
loop	O
bounding	O
,	O
production	O
of	O
human-readable	O
,	O
well	O
commented	O
and	O
well	O
structured	O
code	O
,	O
and	O
avoiding	O
language	O
ambiguities	O
which	O
may	O
lead	O
to	O
compiler-induced	O
inconsistencies	O
or	O
side-effects	O
(	O
expression	O
evaluation	O
ordering	O
,	O
recursion	O
,	O
certain	O
types	O
of	O
macro	O
)	O
.	O
</s>
<s>
These	O
rules	O
can	B-Protocol
often	O
be	O
used	O
in	O
conjunction	O
with	O
code	O
static	O
checkers	O
or	O
bounded	O
model	B-Application
checking	I-Application
for	O
functional	O
verification	O
purposes	O
,	O
and	O
also	O
assist	O
in	O
determination	O
of	O
code	O
timing	B-General_Concept
properties	I-General_Concept
.	O
</s>
<s>
For	O
low-volume	O
or	O
prototype	O
embedded	B-Architecture
systems	I-Architecture
,	O
general-purpose	O
computers	O
may	O
be	O
adapted	O
by	O
limiting	O
the	O
programs	O
or	O
by	O
replacing	O
the	O
operating	O
system	O
with	O
an	O
RTOS	B-Operating_System
.	O
</s>
<s>
In	O
1978	O
National	O
Electrical	O
Manufacturers	O
Association	O
released	O
ICS3-1978	O
,	O
a	O
standard	O
for	O
programmable	O
microcontrollers	B-Architecture
,	O
including	O
almost	O
any	O
computer-based	O
controllers	O
,	O
such	O
as	O
single-board	B-Device
computers	I-Device
,	O
numerical	O
,	O
and	O
event-based	O
controllers	O
.	O
</s>
<s>
Hence	O
it	O
is	O
called	O
a	O
simple	O
control	O
loop	O
or	O
programmed	O
input-output	B-General_Concept
.	O
</s>
<s>
Some	O
embedded	B-Architecture
systems	I-Architecture
are	O
predominantly	O
controlled	O
by	O
interrupts	B-Application
.	O
</s>
<s>
This	O
means	O
that	O
tasks	O
performed	O
by	O
the	O
system	O
are	O
triggered	O
by	O
different	O
kinds	O
of	O
events	O
;	O
an	O
interrupt	B-Application
could	O
be	O
generated	O
,	O
for	O
example	O
,	O
by	O
a	O
timer	O
at	O
a	O
predefined	O
interval	O
,	O
or	O
by	O
a	O
serial	O
port	O
controller	O
receiving	O
data	O
.	O
</s>
<s>
Sometimes	O
the	O
interrupt	B-Application
handler	O
will	O
add	O
longer	O
tasks	O
to	O
a	O
queue	O
structure	O
.	O
</s>
<s>
Later	O
,	O
after	O
the	O
interrupt	B-Application
handler	O
has	O
finished	O
,	O
these	O
tasks	O
are	O
executed	O
by	O
the	O
main	O
loop	O
.	O
</s>
<s>
Cooperative	B-Operating_System
multitasking	I-Operating_System
is	O
very	O
similar	O
to	O
the	O
simple	O
control	O
loop	O
scheme	O
,	O
except	O
that	O
the	O
loop	O
is	O
hidden	O
in	O
an	O
API	B-Application
.	O
</s>
<s>
In	O
this	O
type	O
of	O
system	O
,	O
a	O
low-level	O
piece	O
of	O
code	O
switches	O
between	O
tasks	O
or	O
threads	O
based	O
on	O
a	O
timer	O
invoking	O
an	O
interrupt	B-Application
.	O
</s>
<s>
As	O
any	O
code	O
can	B-Protocol
potentially	O
damage	O
the	O
data	O
of	O
another	O
task	O
(	O
except	O
in	O
systems	O
using	O
a	O
memory	B-General_Concept
management	I-General_Concept
unit	I-General_Concept
)	O
programs	O
must	O
be	O
carefully	O
designed	O
and	O
tested	O
,	O
and	O
access	O
to	O
shared	O
data	O
must	O
be	O
controlled	O
by	O
some	O
synchronization	O
strategy	O
such	O
as	O
message	B-Operating_System
queues	I-Operating_System
,	O
semaphores	B-Operating_System
or	O
a	O
non-blocking	B-Operating_System
synchronization	I-Operating_System
scheme	O
.	O
</s>
<s>
Because	O
of	O
these	O
complexities	O
,	O
it	O
is	O
common	O
for	O
organizations	O
to	O
use	O
an	O
off-the-shelf	O
RTOS	B-Operating_System
,	O
allowing	O
the	O
application	O
programmers	O
to	O
concentrate	O
on	O
device	O
functionality	O
rather	O
than	O
operating	O
system	O
services	O
.	O
</s>
<s>
The	O
choice	O
to	O
include	O
an	O
RTOS	B-Operating_System
brings	O
in	O
its	O
own	O
issues	O
,	O
however	O
,	O
as	O
the	O
selection	O
must	O
be	O
made	O
prior	O
to	O
starting	O
the	O
application	O
development	O
process	O
.	O
</s>
<s>
This	O
timing	O
forces	O
developers	O
to	O
choose	O
the	O
embedded	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
for	O
their	O
device	O
based	O
on	O
current	O
requirements	O
and	O
so	O
restricts	O
future	O
options	O
to	O
a	O
large	O
extent	O
.	O
</s>
<s>
The	O
level	O
of	O
complexity	O
in	O
embedded	B-Architecture
systems	I-Architecture
is	O
continuously	O
growing	O
as	O
devices	O
are	O
required	O
to	O
manage	O
peripherals	O
and	O
tasks	O
such	O
as	O
serial	O
,	O
USB	B-Protocol
,	O
TCP/IP	B-Protocol
,	O
Bluetooth	B-Protocol
,	O
Wireless	B-Architecture
LAN	I-Architecture
,	O
trunk	O
radio	O
,	O
multiple	O
channels	O
,	O
data	O
and	O
voice	O
,	O
enhanced	O
graphics	O
,	O
multiple	O
states	O
,	O
multiple	O
threads	O
,	O
numerous	O
wait	O
states	O
and	O
so	O
on	O
.	O
</s>
<s>
These	O
trends	O
are	O
leading	O
to	O
the	O
uptake	O
of	O
embedded	O
middleware	O
in	O
addition	O
to	O
an	O
RTOS	B-Operating_System
.	O
</s>
<s>
A	O
microkernel	B-Operating_System
allocates	O
memory	O
and	O
switches	O
the	O
CPU	O
to	O
different	O
threads	O
of	O
execution	O
.	O
</s>
<s>
User-mode	O
processes	O
implement	O
major	O
functions	O
such	O
as	O
file	O
systems	O
,	O
network	O
interfaces	B-Application
,	O
etc	O
.	O
</s>
<s>
Exokernels	B-Operating_System
communicate	O
efficiently	O
by	O
normal	O
subroutine	O
calls	O
.	O
</s>
<s>
A	O
monolithic	B-Operating_System
kernel	I-Operating_System
is	O
a	O
relatively	O
large	O
kernel	O
with	O
sophisticated	O
capabilities	O
adapted	O
to	O
suit	O
an	O
embedded	O
environment	O
.	O
</s>
<s>
This	O
gives	O
programmers	O
an	O
environment	O
similar	O
to	O
a	O
desktop	O
operating	O
system	O
like	O
Linux	B-Application
or	O
Microsoft	B-Application
Windows	I-Application
,	O
and	O
is	O
therefore	O
very	O
productive	O
for	O
development	O
.	O
</s>
<s>
On	O
the	O
downside	O
,	O
it	O
requires	O
considerably	O
more	O
hardware	O
resources	O
,	O
is	O
often	O
more	O
expensive	O
,	O
and	O
,	O
because	O
of	O
the	O
complexity	O
of	O
these	O
kernels	O
,	O
can	B-Protocol
be	O
less	O
predictable	O
and	O
reliable	O
.	O
</s>
<s>
Common	O
examples	O
of	O
embedded	O
monolithic	B-Operating_System
kernels	I-Operating_System
are	O
embedded	B-Application
Linux	I-Application
,	O
VXWorks	B-Operating_System
and	O
Windows	B-Operating_System
CE	I-Operating_System
.	O
</s>
<s>
Despite	O
the	O
increased	O
cost	O
in	O
hardware	O
,	O
this	O
type	O
of	O
embedded	B-Architecture
system	I-Architecture
is	O
increasing	O
in	O
popularity	O
,	O
especially	O
on	O
the	O
more	O
powerful	O
embedded	B-Architecture
devices	I-Architecture
such	O
as	O
wireless	B-Device
routers	I-Device
and	O
GPS	B-Application
navigation	I-Application
systems	I-Application
.	O
</s>
<s>
In	O
addition	O
to	O
the	O
core	O
operating	O
system	O
,	O
many	O
embedded	B-Architecture
systems	I-Architecture
have	O
additional	O
upper-layer	O
software	O
components	O
.	O
</s>
<s>
These	O
components	O
consist	O
of	O
networking	O
protocol	O
stacks	O
like	O
CAN	B-Protocol
,	O
TCP/IP	B-Protocol
,	O
FTP	B-Protocol
,	O
HTTP	B-Protocol
,	O
and	O
HTTPS	B-Protocol
,	O
and	O
also	O
included	O
storage	O
capabilities	O
like	O
FAT	B-Application
and	O
flash	B-Device
memory	I-Device
management	O
systems	O
.	O
</s>
<s>
If	O
the	O
embedded	B-Architecture
device	I-Architecture
has	O
audio	O
and	O
video	O
capabilities	O
,	O
then	O
the	O
appropriate	O
drivers	O
and	O
codecs	O
will	O
be	O
present	O
in	O
the	O
system	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
the	O
monolithic	B-Operating_System
kernels	I-Operating_System
,	O
many	O
of	O
these	O
software	O
layers	O
are	O
included	O
.	O
</s>
<s>
In	O
the	O
RTOS	B-Operating_System
category	O
,	O
the	O
availability	O
of	O
the	O
additional	O
software	O
components	O
depends	O
upon	O
the	O
commercial	O
offering	O
.	O
</s>
<s>
In	O
the	O
automotive	O
sector	O
,	O
AUTOSAR	B-Application
is	O
a	O
standard	O
architecture	O
for	O
embedded	O
software	O
.	O
</s>
